The validity of using IP addresses is, as you say, suspect. For instance, I use an ISP that apparently gives me a dynamic IP. If you check this, not only does it change (slightly) but it gives my location as in the UK. I'm in the middle of France! Others who may use the same ISP will come up with similar numbers I suspect. This is especially apparent when one is on a dial-up system as I am - ADSL hasn't found my bit of rural France yet!